Pressure-retentive vessel, e.g. for pressurized-fluid nuclear reactors

ABSTRACT

A pressure-retentive thermally insulated vessel, e.g., for pressurized-fluid nuclear reactors, and a method of making same in which a thin-wall inner shell of corrosion-resistant metal (e.g. stainless steel) is welded from cylinder segments into a hermetically closed container. The outer shell of the double-wall lining, whose interwall space is filled with a force-transmitting thermally insulating material (e.g. a low heat-conductivity concrete), is welded together of cylinder segments of heavy-gauge steel. To support the inner wall, a plurality of radial angularly and axially spaced tie rods are welded to the outer surface of the thin inner vessel, passed through openings in the outer wall, and engage in the surrounding body of concrete serving as the outer support and radiation-shielding mass. The openings are sealed by welding and the rods are rigidly fixed to the outer wall, e.g. via bridge plates overlying the openings.

United States Patent 1 Meyer et al.

[4 1 Jan. 16,1973

[54] PRESSURE-RETENTIVE VESSEL, E.G. FOR PRESSURIZED-FLUID NUCLEARREACTORS [75] Inventors: Joachim Meyer; Josef Pfeffer, both of Essen,Germany [73] Assignee: Fried. Krupp GmbH, Essen, Germany [22] Filed: May4, 1970 [21] Appl. No.2 34,081

[52] US. Cl ..165/169 [51] Int. Cl. .4 ..F28f 3/12 [58] Field of Search..l65/47, 136, 169

[56] References Cited UNITED STATES PATENTS 3,454,080 7/1969 Kunzli..l65/l36 X 3,424,239 1/1969 Coudray ..l65/l69 X Primary Examiner-John.l. Camby Attorney-Karl F. Ross [57] ABSTRACT A pressure-retentivethermally insulated vessel, e.g., for pressurized-fluid nuclearreactors, and a method of making same in which a thin-wall inner shellof corrosion-resistant metal (e.g. stainless steel) is welded fromcylinder segments into a hermetically closed container. The outer shellof the double-wall lining, whose interwall space is filled with aforce-transmitting thermally insulating material (e.g. a lowheat-conductivity concrete), is welded together of cylinder segments ofheavy-gauge steel. To support the inner wall, a plurality of radialangularly and axially spaced tie rods are welded to the outer surface ofthe thin inner vessel, passed through openings in the outer wall, andengage in the surrounding body of concrete serving as the outer supportand radiation-shielding mass. The openings are sealed by welding and therods are rigidly fixed to the outer wall, e.g. via bridge platesoverlying the openings.

6 Claims, 5 Drawing Figures PATENTED AH 1 I 7 3.710.857

SHEET 1 BF 3 Inventors:

JOACH/M MEYER JOSEF PFEFFER ATTOPHEY PATENTEUJAN 16 I975 SHEET 2 [IF 3INVENTORS:

JOACHIM MEYER BY JOSEF PFEFFER gear! 9'- ATTORNEY PATENTEUJAH 16 1975SHEET 3 0F 3 INVENTORS JOACHIM MEYER BY JOSEF PFEFFER 90,1 ATTORNEYPRESSURE-RETENTIVE VESSEL, EG. FOR PRESSURIZED-FLUID NUCLEAR REACTORSFIELD OF THE INVENTION Our present invention relates topressure-retentive and thermally insulating vessels, to a method oferecting such vessels, to improved lining structures for theseBACKGROUND OF THE INVENTION It hasbeen proposed in reactor technology toprovide massive reactor structures of concrete or the like which arecast about a vessel or lining so as to constitute a structural supportfor the metallic lining to the extent necessary to retain any criticalor leakage event while, at the same time, serving as a radiation shield,adapted to restrict radiation flux from the interior of the reactor topopulated environments therearound.

The vessel heretofore used for this purpose, comprised a massiveprestressed concrete outer body which also provided a metallic liningadapted to contain the radiation materials, i.e., leaked radioactivefuels, fission products, irradiated materials, etc.

Such prestressed-concrete containment vessels for nuclear reactors havenumerous advantages. Firstly, this mode of construction offersconsiderable freedom of choice in the size, shape and pressure-retentiveor loading capacity of the structure. Secondly, concrete inherently isan excellent shielding material with a low failure rate and relativelyhigh shielding capacity per unit thickness of any shielding wallconstructed therefrom. Thirdly, any danger of diffusion or leadage ofradioactive materials through the concrete, which occasionally with timemay become more or less permeable, is precluded by the inner liningstructure.

One of the primary disadvantages of conventional metal-lined, reinforcedand/or prestressed concrete vessels is that, while the reinforcedconcrete mass surrounding the metal lining is an' effective insulation,the

' concrete cannot withstand temperatures in or above and above, as mayarise in nuclear-reactor applications. It is not a solution, from apoint of view of the economics of the nuclear-reactor art, to employmassive metal linings of corrosion-resistant materials such as stainlesssteel and, indeed such steels, when provided in the massive thicknessesrequired for pressure retention, are increasingly likely to be subjectto stress crack, corrosion and the like at the elevated temperatures atwhich the reactor operates.

OEJECT OF THE INVENTION It is, therefore, the principal object of thepresent invention to'provide an improved wall structure for pressurevessels in which the aforementioned disadvantages can be avoided.

Another object of this invention is the provision of apressure-retentive, thermally insulating vessel of relatively low costand yet excellent resistance to corrosion at the enclosed chamber,resistance to stress as may be result from pressure within, and ofthermal transmissibility.

Another object of our invention is to provide a metal liner system forprestressed-concrete pressure vessels enabling them to be usedeffectively with corrosive high temperature fluids, e.g., influid-cooled nuclear reactors, in an economical and practical manner.

Still further, it is an object of this invention to provide an enclosurefor a gas-pressure, pressurized-water or other nuclear reactor operatingunder elevated fluid pressure.

It is also our object to provide an improved method of making astructure of the general character described which is capable ofretaining elevated pressures, manifests a high degree of thermallyinsulating capability, is hermetically sealed to preclude escape ofradioactive or other materials, is substantially noncorrodible and iseconomical to construct.

SUMMARY OF THE INVENTION These objects and others, which will becomeapparent hereinafter, are attained, in accordance with the presentinvention, through the provision of a pressureretentive vessel whichincludes a massive body of concrete surrounding the enclosed chamber,and a lining structure interposed between this body and and the chamber,the lining being of the double-wall type and comprising an inner,relatively thin sheet-metal shell of a metal of low corrodibility,welded from cylindrical segments into an inner vessel preventing escapeof active materials from the compartment enclosed thereby. Thisthin-walled vessel constitutes a membrane which can be flexed bypressure within the vessel and we provide therefore, as alow-thermal-conductivity means for transmitting the forces from theinner vessel to the outer vessel, a multiplicity of angularly equispacedrods which may be axially distributed as well and preferably have athickness (diameter) equal to or approximating the wall thickness of theinner vessel, the rods being substantially rigidly affixed to the outer,relatively thick metal shell, likewise welded together from cylindersegments and composed of a structural metal which need not be asexpensive as the noncorroding metal of the inner shell.

The present invention thus provides a pressure-vessel liner which can beexposed to a fluid medium at high temperature and of a corrosive nature,may be .subjected to high internal temperatures without increasing thedanger of failure of the noncorroding inner liner, and may be usedwithout the danger that the temperature along the outer wall of thedouble-wall liner will reach to C and becomes detrimental to thesurrounding concrete body, while enabling the entire assembly to beerected at the construction site in whole or in part prior to casting ofthe prestressed concrete outer mass.

The invention may thus include a concentric (coaxial) liner arrangement,the inner wall of which is composed of corrosion-resistant material,e.g., stainless by a multiplicity of small cross-section membersdefining a substantially rigid structure. The supporting members serveto limit the span of the inner wall which is subject to outward bucklingpressure from the enclosed fluid. When the distance (angular or axial)between these generally radial members is sufficiently small, thethickness of the inner wall can be reduced to a very samll fraction ofthat of the outer wall. Preferably, the inner liner has a thicknesswhich is less than half that of the outer liner.

The several components of the double-wall structure may be fabricatedand partially assembled in a steelfabrication plant and moved to theconstruction site in easily transported subassemblies. At theconstruction site, the segments are joined by deposit-weld seams to formthe complete liner structure, whereupon concrete is cast around theliner and stressed in the conventional manner.

According to a more specific feature of this invention, the outer shellis formed with openings through which the connecting members extend, theclearance between the members and the walls of the openings beingblocked by bridge pieces welded along the outer surface of the shell.The connecting rods themselves are preferably welded to the outersurface of the inner vessel. Advantageously, projecting portions of themembers extend beyond the outer wall of the outer shell and into thesurrounding concrete body where they are anchored in the matrix of theconcrete vessel and serve to transmit the internal-pressure load to theshell.

Still another feature of this invention resides in the filling of theinterwall space with a rigid insulating material, e.g., so-calledinsulating concrete, serving to reduce transmission of heat to the outervessel and, therefore, the concrete body therebeyond. This rigidinsulation layer although serving as an additional force-transmittingmedium between inner and outer shells, can be subject to deteriorationat elevated temperatures since the radial members or spokes aredimensioned to take up the full operational load plus an additionalsafety factor as if the insulating layer had no force-transmittingcapability.

Still another feature of the invention resides in the provision at theouter vessel or wall of coolant channels designed to maintain theinterface between the surrounding concrete body and the outer metalshell at a temperature below 70 to 80 C, when the insulating qualitiesof the double-wall structure do not suffice.

DESCRIPTION OF THE DRAWING The above and other objects, features andadvantages of the present invention will become more readily apparentfrom the following description, reference being made to the accompanyingdrawing in which:

FIG. 1 is a horizontal cross-sectional view through a pressure-retainingvessel according to this invention;

FIG. 2 is a vertical section along this line II II of FIG. 1:

FIG. 3 is a diagram illustrating the manner in which the variouscomponents are assembled to form the liner;

FIG. 4 is a detail view illustrating a modified construction of thesupport arrangement; and

FIG. 5 is a vertical elevational view, partly broken away, of apressure-retentive vessel in accordance with the present invention.

SPECIFIC DESCRIPTION As will be apparent from FIGS. 1 and 2, the basicvessel structure comprises a concrete body 6 of the prestressed andreinforced type commonly used to surround nuclear reactors of thegas-pressure or pressurized-wa ter type and formed with a metal shell.The conventional shell is, in accordance with the present invention,replaced by a double-wall shell whose interwall space' 7 can be filledwith expanded concrete, lightweight or cellular concrete, concrete madewith expanded perlite aggregates and like insulating concretes.

The basic lining structure comprises a hermetically sealed thinstainless-steel inner liner 2, formed from a plurality of cylindersegments 1a, lb, 10 and joined by welds 9, here shown to be formed fromthe inside during assembly of the inner liner at a steel-fabricationplant or, from preassembled parts, at the construction site.

Along the exterior surface of the shell I, we provide closely spacedradial spokes 2 which are welded at 20 to the inner vessel and protrudethrough corresponding holes 3 in the relatively thick structural-steelouter liner 4. The latter is welded from the exterior into a sealedstructure along weld seams of conventional type from a plurality ofcylindrical segments. The supporting members 2 are rigidly connected tothe outer liner 4 by being welded to bridge pieces 5 which, in turn, arewelded to the outer liner to completely seal the openings 3. Beyond thebridge pieces 5, the spokes 2 are extended by anchors 2' welded orotherwise connected to the spokes 2 and having outwardly flaredbifurcated ends embedded in the concrete matrix 6. During the slightexpansion and contraction of the inner vessel, the rods may manifest aslight twist or lateral movement with the flexural limits of rod andbridge piece and centered a substantially at the intersection of thetwo, each bridge piece functions to this extent at least, as a membraneelastically permitting such movement while each rod forms a leaf spring.The lateral deflectibility of the rods within the elastic limit isgreater with bridge plates secured to the outer periphery of the outershell than when the rods are secured directly to the outer shell or to abridge piece disposed along the inner surface.

The space 7 between the inner wall 1 and the outer wall 4 is filled withthe expanded concrete 10 serving both as insulating and as atransmission means for the loads produced by the internal pressureacting on the inner liner and any compensatory no-load prestress appliedby the outer concrete matrix. Coolant channels 8, in the form of helicaltubes coiled around the outer wall between the spokes 2 and welded tothis wall for maximum heat transfer, are provided to remove any heatconducted through the insulating material 10 and the spokes 2, as may berequired to reduce the temperature along the interface with the concretebody 6 below the level of to C.

The liner assembly as described is constructed in a number of segments,each preferably covering one quarter a quadrant) of the circumference ofthe cylindrical shell. Four of these subassemblies are connected bymeans of welds 9a, 9b, 9c and 9d to form a ring and several such ringsare' joined by horizontal welds, such as 9e in FIG. 2, to form thecomplete vessel.

The subdivision into four arcuate segments is arbitrary, but at leastone of the inner or outer liners must be segmented to permit allassembly welds to be completed from the inside of the inner wall or theoutside of the outer wall.

FIG. 3 indicates the method of manufacturing a single subassembly.Supporting members 2 are first welded radially to inner wall 1 whichencompasses an arc of magnitude :.A corresponding section of the outerwall 4 is then brought near the segment of the inner wall 1 and the twomoved together along the bisecting radius B B, in such a manner that theradiating supporting members 2 move through holes 3 in the outer wall 4.Because of the angle B included between the line of movement and theoutermost supporting member the holes 3 must be larger (angular extent-y) than the corresponding cross-sections of the supporting members 2,the rigidity of the assembly being insured by the bridge pieces 5. Thearc a should not substantially exceed a right angle for easy assembly;if it is restricted to angles much smaller than this, the clearancebetween supporting members 2 and holes 3 may be made small enough topermit bridging by means of the weld bead and the elimination of bridgepieces 5 from the assembly.

As will be apparent from FIG. 4, the sheet-metal inner wall 30 may bewelded to spokes 31 at seams 32, but the connection of these spokes tothe outer wall 33 may be accomplished without bridge plates. in thisconnection arrangement, the outer wall 33 is clamped between a nut 34along the inner surface, threaded onto the spoke 31 and a washer 35 heldby a rod 36 threaded onto the spoke 31 from the exterior. Therod 36 hasa bifurcated end to form the extension of the spoke which is anchored inthe concrete.

In FIG. 5, there is shown a structure in which the cylindrical segments38 and 39 are so closely spaced or so numerous that the spokes 40 passthrough the gaps between them, the gaps being welded closed asrepresented at 41. in this embodiment, the inner vessel 42, theintervening layerof insulating concrete 43, the outer vessel 44 and theouter concrete layer 45 are all illustrated and constituted aspreviously described.

It has been found that, for power reactors operating at 500 to 1000 MW,it is desirable to use pressure vessels with an internal diameter of mor more. The inner liner is here made in cylinder segments of a maximumof 90 of arc while the radial spokes are distributed around thecircumference in ISO to 200 in number and at the corners of squares 0.3m on a side.

An important advantage of the present invention resides in the fact thatcylindrical segments of the inner wall and corresponding segments of theouter shell may be united, with the respective spokes therebetweenserving as connecting means. The resulting structure, for example asillustrated in FIG. 3, is a hollow-wall vessel segment which may betransported to the construction site and erected there, together withsimilar hollow-wall vessel segments, into a complete tank, theinner-shell members of the hollow-wall vessel segments being-joined byinternal welds and the outer-shell members being joined by externalwelds. The space between the now-completed inner and outer walls maythen be filled with insulating concrete.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodification being considered within the spirit and scope of theinvention except as limited by the appended claims.

We claim:

1. A pressure-retentive vessel, comprising:

a liner enclosing a pressure compartment and including apressure-retentive sealed, relatively thin inner wall ofcorrosion-resistant material directly enclosing said compartment, arelatively thick outer wall spacedly surrounding said inner wall andenclosing same, and a multiplicity of outwardly extending rod memberswelded to said inner wall perpendicular thereto and substantiallyrigidly fixed to said outer wall for force-transmission between saidouter and inner walls;

a reinforced concrete body surrounding said liner, each of said wallsbeing of substantially cylindrical configuration and being composed of aplurality of cylinder segments joined along respective weld seams, saidrod members extending radially from the inner wall to the outer wall;

a plurality of generally outwardly extending anchors formed on saidouter wall and embedded in said body, and each formed as an extension ofone of said rod members, said rod members projecting through said outerwall, said lining being further formed with cooling channels forconduction of a cooling fluid therethrough, said outer wall being formedwith respective openings of a cross-section in excess of thecross-section of the respective rod member and said rod membersextending with clearance through said openings, said liner furthercomprising bridge pieces welded to said outer wall along the outersurface thereof and closing said clearances.

2. The vessel defined in claim 1 wherein said members pass throughopenings 'in and are each sealingly welded to said bridge pieces aboutthe peripheries of said rod members.

3. The vessel defined in claim 2, further comprising a rigid insulatingmass received in the space between said walls. I

4. The vessel defined in claim 3 wherein said rod members are ofcircular cross-section.

5. The vessel defined in claim 4 wherein said vessel is anuclear-reactor enclosure and said inner wall is composed of stainlesssteel and has a thickness less than half the thickness of said outerwall, said outer wall being composed of structural steel, saidinsulating means consisting of insulating concrete, said coolingchannels including tube means coiled around said outer wall and inheat-conducting relation therewith.

6. A method of making the vessel defined in claim 5, comprising thesteps of fabricating a plurality of cylindrical inner-wall segments fromstainless steel, and a plurality of cylindrical outer wall segments fromstructural steel while forming a multiplicity of openings in said outerwall segments; at a location remote from the vessel site welding aplurality of generally radial metal spokes to the exterior of at leastone inner-wall seg- LII welding to the outer-wall segments of saidhollow-wall vessel Segments together; filling the space between theinner wall formed by said inner-wall segments and the outer wall formedby said outer-wall segments with a rigid thermal insulating material;and casting a concrete body around said outer wall.

1. A pressure-retentive vessel, comprising: a liner enclosing a pressurecompartment and including a pressure-retentive sealed, relatively thininner wall of corrosion-resistant material directly enclosing saidcompartment, a relatively thick outer wall spacedly surrounding saidinner wall and enclosing same, and a multiplicity of outwardly extendingrod members welded to said inner wall perpendicular thereto andsubstantially rigidly fixed to said outer wall for force-transmissionbetween said outer and inner walls; a reinforced concrete bodysurrounding said liner, each of said walls being of substantiallycylindrical configuration and being composed of a plurality of cylindersegments joined along respective weld seams, said rod members extendingradially from the inner wall to the outer wall; a plurality of generallyoutwardly extending anchors formed on said outer wall and embedded insaid body, and each formed as an extension of one of said rod members,said rod members projecting through said outer wall, said lining beingfurther formed with cooling channels for conduction of a cooling fluidtherethrough, said outer wall being formed with respective openings of across-section in excess of the cross-section of the respective rodmember and said rod members extending with clearance through saidopenings, said liner further comprising bridge pieces welded to saidouter wall along the outer surface thereof and closing said clearances.2. The vessel defined in claim 1 wherein said members pass throughopenings in and are each sealingly welded to said bridge pieces aboutthe peripheries of said rod members.
 3. The vessel defined in claim 2,further comprising a rigid insulating mass received in the space betweensaid walls.
 4. The vessel defined in claim 3 wherein said rod membersare of circular cross-section.
 5. The vessel defined in claim 4 whereinsaid vessel is a nuclear-reactor enclosure and said inner wall iscomposed of stainless steel and has a thickness less than half thethickness of said outer wall, said outer wall being composed ofstructural steel, said insulating means consisting of insulatingconcrete, said cooling channels including tube means coiled around saidouter wall and in heat-conducting relation therewith.
 6. A method ofmaking the vessel defined in claim 5, comprising the steps offabricating a plurality of cylindrical inner-wall segments fromstainless steel, and a plurality of cylindrical outer wall segments fromstructural steel while forming a multiplicity of openings in said outerwall segments; at a location remote from the vessel site welding aplurality of generally radial metal spokes to the exterior of at leastone inner-wall segment, fitting an outer-wall segment spacedly aroundthe inner-wall segment and welding said spokes thereto, thereby forminga hollow-wall vessel segment; assembling a plurality of such hollow-wallvessel segments into a final vessel configuration at the vessel site andinternally welding the inner-wall segments of the hollow-wall vesselsegments together and externally welding to the outer-wall segments ofsaid hollow-wall vessel segments together; filling the space between theinner wall formed by said inner-wall segments and the outer wall formedby said outer-wall segments with a rigid thermal insulating material;and casting a concrete body around said outer wall.